Much has been written on the topic of stress & disease, below is summary to help guide you throughout
Skin / Gill Flukes prevention and identification. Please feel free to send any comments or suggestions to Ask An Expert.

Like many parasitic diseases, the fish is not likely to be affected unless it is stressed or sick. They are tiny worm-like parasites that are rarely seen by the naked eye. They attach to the fish with hooks-like structures and whilst attached can actually move around! They affect mainly young fish, older fish seem to be less affected. The parasite spreads quickly in an aquarium, so quick treatment is preferable.

The parasite can kill fish in large numbers, and secondary infections are also a common cause of death.

Skin / Gill Flukes Treatments

Flukes are hard to treat and complete eradication is virtually impossible. For individuals affected with flukes, consecutive salt baths over 2-3 days can be useful.

Skin / Gill Flukes Prevention

Make sure the water is of a high quality, check pH and ammonia levels.